Abstract [en]

Electrical interconnections are one of the main challenges in the printed electronics, to connect different functional units of an electronic device. With the progressive advancement of large area and low cost printed electronic devices on polymeric and paper substrates, the requirement for reliable interconnections with lower power consumption fabricated at low temperature is necessary. The conventional copper-based interconnections suffer severe problems in terms of cost efficiency when they are processed with photolithography technique. To replace the conventional metallic interconnections we have proposed printed interconnects with graphene inks. This is mainly motivated by two reasons. First, printing is a low-cost patterning approach which is performed at ordinary ambient condition. Printing of graphene proved to be a promising since it combines the attractive features of graphene and the cost effective printing methods (ink-jet printing, nozzle printing, spray printing) which enable additive patterning, direct writing, scalability to large area manufacturing. In order to facilitate the inkjet printing process, the graphene solution needs to be highly stable, uniform and should contain smaller sheet sizes (~ 1 micro meter) because of the limitation of the nozzle size of inkjet printing machine. In this work we have proposed a cost-effective approach for large-scale production of printable stable graphene suspension by liquid-phase shear exfoliation of graphite for printed electronics application. The process is scalable and requires shorter processing time compared to the other existing exfoliation methods. Graphene sheets have been exfoliated from graphite flakes in a solvent, cyclohexanone with ethyl cellulose as stabilizer. The graphene based solution prepared after several optimizations leads to a stable ink for more than six months without any sedimentation. The initial studies confirmed the production of graphene films with average sheet thickness of 10 to 20 nm and without any agglomeration with sheet sizes less than 1 micro meter. The rheological properties, such as, viscosity, of the produced graphene ink has been carefully tuned in order for successful inkjet printing process. Highly conductive and transparent (~70 % in the visible region) interconnections have been developed after several inkjet printing steps.